The two UAE leaders reiterated the importance of stepping up regional and global coordination to combat extremism and terrorism and to block their financing sources.

Kuwait's emir Sheikh Sabah Al-Ahmad Al-Jaber Al-Sabah will meet with Saudi Arabia's King Salman and help mediate what has shaped up to be the worst dispute among regional powers in decades.

The Emir was aiming to mediate in the dispute between Qatar and its Gulf neighbours led by Saudi Arabia, lawmakers in Kuwait City said earlier.

During a telephone call with Qatari Emir Tameem Bin Hamad al-Thani, U.S. President Donald Trump offered assistance in helping the parties reconcile, including through a White House meeting "if necessary", the executive mansion said in a readout of the call.

Asked for specifics about what Arab nations wanted from Qatar, Gargash said expelling members of Hamas and other groups from Qatar was important.

Qatar Airways has subsequently suspended all flights to the UAE, Saudi Arabia, Bahrain and Egypt, while those nations have closed their airspace to Qatar Airways.

Qatar long has denied funding extremists, although Western officials have accused it of allowing or even encouraging funding of Sunni extremists like al-Qaida's branch in Syria, once known as the Nusra Front.

The Qatari Foreign Ministry said in a statement the two held talks on how "restore the normal relations" of the Gulf as the 2022 FIFA World Cup host and worldwide air travel hub now finds itself isolated by land, sea and air.

"On this scale, it's unprecedented", said Hatoon al-Fassi, a Saudi historian of Gulf Affairs and Women's Studies at Qatar University.

On Monday Kuna news agency, an official state news service based in Kuwait, confirmed the phone call between the two leaders. "It reveals a hidden plan to undermine the State of Qatar", the statement said.

Qatar strongly rejects the allegations.

The Gulf countries forbade their citizens from traveling to Qatar, residing in it or passing through it, instructing their citizens to leave Qatar within 14 days and gave Qataris 14 days to leave those countries. In the alleged hack, Qatar News Agency published a news report that criticized USA foreign policy, the United Arab Emirates, Bahrain and Egypt, and defended Hezbollah, Hamas and Iran.

Qatar "believes such differences between sister countries must be resolved through dialogue", Sheikh Mohammed added.

The ministry did not say who it suspected carried out the attack, though it thanked the FBI and the British National Commission for Combating Crime for assisting it in its investigation.

The head of Iran's agricultural products export union on Monday said Tehran was ready to fend off potential food shortages with exports to Qatar by sea.

The Saudi ports authority said Qatari-flagged shipping vessels are barred from docking.